With respect to a digital data recording sheet and a digital data reader for reading the recording sheet, applicant has invented "Identification Code Sheet" Japanese Patent Application No. Sho 62-173352 (1987) and "Identification Code Reader" Japanese Patent Application Laid Open No. Sho 64-76176 (1989), which have been published in the aforesaid official gazettes.
In the inventions stated above, an identification code sheet for facilitating the display of JIS codes, relative to Chinese characters by displaying binary data of four or more bits in two directions is disclosed, and an identification code reader for accurately reading the digital data is disclosed by delineating a mark area with division marks and recording the binary data in the mark area.
Moreover, applicant has invented "Digital Data Recording Sheet and Method of Digital Data Communication", Japanese Patent Application No Hei 1-51971 (1989). This application discloses a long distance communication method for communication such as FAX transmissions using the recording sheet, wherein the mark area is delineated by the division marks and binary data is recorded in the mark area.
In the published applications discussed above, errors due to variations in the mark area occur due to expansion and contraction of the recording sheet and changes in paper feeding speed during communication and FAX transmission. Errors in the marks on the digital data recording sheet can be corrected by the prior inventions. However, when the position of the division marks is varied from the original display position due to expansion and contraction of the recording sheet or changes in the recording sheet feeding speed, reading the binary signal mark indicated in the mark area is difficult.
Therefore, it is an object of the first to fourth embodiments of the present application to correct for deformations of the display area without using division marks. It is an object of the fifth embodiment of the present application to ensure detection of the division marks.